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A polymer coating autonomously reports damageviafluorescence from a force-induced retro-Diels–Alder reaction. The optical signal correlates with impact energy, enabling real-time, equipment-free damage detection, even in pigmented coatings. 

Fluorinated polymers are important functional materials for a broad range of applications, but the recycling of current fluorinated polymers is challenging. We present the first example of semi-fluorinated polymers that can undergo chemical recycling to form the corresponding monomers under ambient conditions. Prepared through ring-opening metathesis polymerization of functionalized trans -cyclobutane fused cyclooctene ( t CBCO) monomers, these polymers show tunable glass transition temperatures (−2 °C to 88 °C), excellent thermal stability (decomposition onset temperatures >280 °C) and hydrophobicity (water contact angles >90°). The hydrophobicity of the semi-fluorinated polymers was further utilized in an amphiphilic diblock copolymer, which forms self-assembled micelles with a size of ∼88 nm in an aqueous solution. Finally, through an efficient, regioselective para -fluoro-thiol substitution reaction, post-polymerization functionalization of a polymer with a pentafluorophenyl imide substituent was achieved. The ease of preparation, functionalization, and recycling, along with the diverse thermomechanical properties and demonstrated hydrophobicity make the t CBCO-based depolymerizable semi-fluorinated polymers promising candidates for sustainable functional materials that can offer a solution to a circular economy. 

Abstract Polymers with low ceiling temperatures (T_c) are highly desirable as they can depolymerize under mild conditions, but they typically suffer from demanding synthetic conditions and poor stability. We envision that this challenge can be addressed by developing high-T_cpolymers that can be converted into low-T_cpolymers on demand. Here, we demonstrate the mechanochemical generation of a low-T_cpolymer, poly(2,5-dihydrofuran) (PDHF), from an unsaturated polyether that contains cyclobutane-fused THF in each repeat unit. Upon mechanically induced cycloreversion of cyclobutane, each repeat unit generates three repeat units of PDHF. The resulting PDHF completely depolymerizes into 2,5-dihydrofuran in the presence of a ruthenium catalyst. The mechanochemical generation of the otherwise difficult-to-synthesize PDHF highlights the power of polymer mechanochemistry in accessing elusive structures. The concept of mechanochemically regulating theT_cof polymers can be applied to develop next-generation sustainable plastics. 

Abstract The accumulation of plastic waste, due to lack of recycling, has led to serious environmental pollution. Although mechanical recycling can alleviate this issue, it inevitably reduces the molecular weight and weakens the mechanical properties of materials and is not suitable for mixed materials. Chemical recycling, on the other hand, breaks the polymer into monomers or small‐molecule constituents, allowing for the preparation of materials of quality comparable to that of the virgin polymers and can be applied to mixed materials. Mechanochemical degradation and recycling leverages the advantages of mechanical techniques, such as scalability and efficient energy use, to achieve chemical recycling. We summarize recent progress in mechanochemical degradation and recycling of synthetic polymers, including both commercial polymers and those designed for more efficient mechanochemical degradation. We also point out the limitations of mechanochemical degradation and present our perspectives on how the challenges can be mitigated for a circular polymer economy. 

Abstract Helices are unique structures that play important roles in biomacromolecules and chiral catalysis. The mechanochemical unfolding of helical structures has attracted the attention of chemists in the past few years. However, it is limited to a few cases which investigated how the mechanochemical reactivity is impacted by helical configurations. No synthetic helical mechanophore is reported. Herein, a Zn (II) bidipyrrin (BDPR‐Zn) double helix is designed as a potential mechanophore. A cyclic olefin containing a doubly strapped BDPR‐Zn is prepared and used for ring‐opening metathesis polymerization. The corresponding polymer is subjected to pulsed ultrasonication for mechanochemical testing. The sonication results reveal the mechanochemical inertness of BDPR‐Zn unit, which is further supported by force‐coupled simulation. Although no obvious activation is observed, our preliminary results on BDPR‐Zn unit could inspire further rational designs on force‐induced helix unfolding.